1. Port group model in G.8021 Akira Sakurai G.8021 Co-editor IEEE 802.1 and ITU-T Q.9/15 Ethernet Transport issues (Geneva, 27 May 2010)

2. Background The introduction of the Port Group construct in Ethernet Flow Forwarding (ETH_FF) process in ITU-T Recommendation G.8021 Amendment 2 is based on 12 months study and the development of a set of requirements based on carriers and vendors contributions to support E-Tree and E- LAN services. These services have already been specified in G.8011.x series of Recommendations. G.8011 - Ethernet Services Framework G.8011.4 - Ethernet Virtual Private Rooted Multipoint Service G.8011.5 - Ethernet Private LAN Service

3. Requirements for E-Tree/E-LAN services 1. A single Ethernet Virtual Connection (EVC) to support E-Tree and E-LAN services 2. Capability to reduce latency in EVC 3. Capability to support Y.1731 OAM for EVC and server/EVC adaptation functions located in NNI ports 4. Capability to traffic-engineered rmp and mp2mp EVCs by means of performing Traffic Conditioning (TC) at the ingress of each EVC link connection 5. Support of EVC by a mix of server layer technologies such as: ETH MPLS-TP SDH VC-n OTN ODUk

4. Principle of the Port Group Frames arriving via an input port in a Port Group may be forwarded to one or more output ports, with the exception of the output ports that are member of the Port Group. Frames arriving on an input port which is not a member of the Port Group may be forwarded to one or more output ports, with exception of the port over which the frame arrived. A B C X Y Z Port Group {A,B,C} ETH_FF {A,B,C,X,Y,Z}

5. Applications for the Port Group Primary is to allow for configuration of a rooted-multipoint EVC. Additional application is Split horizon. Rooted multipoint EVC Split horizon Root Leaf Port group

6. Reduction of latency Full mesh of ETH VC link connections in a domain contributes to the reduction of latency for forwarding frames. However, it does require an additional loop-prevention mechanism. The Port Group performs this mechanism at the bridging points without changing any of MEP/MIP/TC functionalities.

7. Location of the Port Group functionality Option1 - between the ETH_FF process and the ETH MEP/MIP/TC functions in the interface ports The Port Group functionality is collocated with the original ETH_FF process inside an ETH Connection (ETH_C) function. Option 2 - inside a Server/ETH_A function This does not support the possibility of traffic conditioning at the Ingress of the EVC link connections, nor the use of different server layer technologies. For these reasons, G.8021 selected the option 1 to achieve the Port Group functionality. Option1 ETH_FF Srv/ETH Srv ETH Srv/ETH Srv ETH Srv/ETH Srv ETH Srv/ETH Srv ETH ETH_FF Srv/ETH Srv ETH ETH/ETHm ETH_C Option2

8. Conclusion The introduction of the Port Group defined in G.8021 Amd2 enables operators to deploy E-Tree/E-LAN services efficiently. ITU-T SG15 Q9 would like to express its appreciation for the continued useful exchange of information with IEEE 802.1 on Ethernet technology standards. We look forward to continuing this coordination in the future.